Panels comprising a mechanical locking device and an assembled product comprising the panels

ABSTRACT

A set of panels includes a first panel having a first main plane and a second panel having a second main plane. The panels are provided with a mechanical locking device for locking a first edge of the first panel to a second edge of the second panel. The mechanical locking device includes an edge groove at the first edge, wherein an edge tongue of the second edge is insertable into the edge groove. A flexible tongue is arranged in an insertion groove provided in the edge section groove, and cooperates with a tongue groove provided at the edge section of the second panel. The first and the second panels are locked at a junction plane which is extending between the first main plane and the second main plane. The first edge comprises an edge tongue that extends from the junction plane.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of Swedish Application No.1451611-6, filed on Dec. 19, 2014. The entire contents of SwedishApplication No. 1451611-6 are hereby incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to panels that may be arrangedperpendicular to each other and locked together with a mechanicallocking device. The panels may be assembled and locked together toobtain a furniture, such as a bookshelf, a cupboard, a wardrobe, akitchen fixture, a box, a drawer or a furniture component. The lockingdevice may comprise a flexible tongue.

BACKGROUND

A furniture provided with a mechanical locking device is known in theart, as evidenced by WO2012154113(A1). The furniture comprises a firstpanel connected perpendicular to a second panel by a mechanical lockingdevice comprising a flexible tongue in an insertion groove.

SUMMARY

One object of certain embodiments of the present invention to provide animprovement over the above described technique and the known art. Aspecific objective is to improve the strength of a mechanical lockingdevice at a mitre joint of an assembled product, such as a furniture, afurniture component, a drawer, a cupboard, a bookshelf, a wardrobe, akitchen fixture, or a box for storing or transporting.

A further object of certain embodiments of the invention is to provide afurniture product with increased strength and stability.

At least some of these and other objects and advantages that will beapparent from the description have been achieved by a set of panelscomprising a first panel with a first main plane and a second panel witha second main plane, wherein the first and the second panel are providedwith a mechanical locking device for locking a first edge of the firstpanel to a second edge of the second panel at a junction plane. Thefirst main plane is essentially perpendicular to the second main planeand the junction plane is extending between the first main plane and thesecond main plane. The first edge comprises an edge tongue, whichextends from the junction plane. The second edge comprises an edgegroove at the junction plane, wherein the edge tongue is configured tocooperate with the edge groove for locking together the first and thesecond edges in a first direction which is parallel to the junctionplane. The edge tongue comprises a tongue groove and the edge groovecomprises a flexible tongue arranged in an insertion groove, saidflexible tongue is configured to cooperate with the tongue groove forlocking together the first and the second edges in a second directionwhich is perpendicular to the junction plane.

This configuration provides large locking and contact surfaces and arigid locking of the panels may be obtained.

The angle between the junction plane and the first main plane ispreferably about 45°. A different angle may be preferred for a set withdifferent thicknesses of the first and the second panel. The angle ispreferably adapted such that the junction plane extends through anintersection of an outer face of the first panel and an outer face ofthe second panel to an intersection of an inner face of the first paneland an inner face of the second panel. The inner face of the first panelis facing the inner face of the second panel. An outer face of the firstpanel is opposite to the inner face of the first panel. An outer face ofthe second panel is opposite to the inner face of the second panel.

The edge tongue may extend essentially perpendicular from the junctionplane.

The edge tongue at the junction plane may comprise a first surface andan opposite second surface, wherein the first and the second surfacesare preferably parallel.

The first surface and the opposite second surface are preferablyessentially perpendicular to the junction plane.

The edge groove at the junction plane may comprise a third surface andan opposite fourth surface, wherein the third and the fourth surfacesare parallel to the first surface and to the second surface. The firstsurface is preferably configured to cooperate with the third surface andthe second surface is preferably configured to cooperate with the fourthsurface for a locking in the first direction.

The edge tongue may comprise a fifth surface and an opposite sixthsurface at the tip of the tongue, wherein the fifth and the sixthsurfaces are parallel.

The fifth surface and the opposite sixth surface are preferablyessentially perpendicular the junction plane.

The edge groove may comprise a seventh surface and an opposite eighthsurface at a bottom of the edge groove, wherein the seventh and theeight surfaces are parallel to the fifth surface and the sixth surface.The fifth surface is preferably configured to cooperate with the seventhsurface and the sixth surface is preferably configured to cooperate withthe eight surface for a locking in the first direction.

The parallel surfaces may further increase the strength of the lockingsystem and the stability of an assembled furniture product provided withthe mechanical locking device.

The insertion groove may be arranged parallel to the second main planeor at an acute angle, wherein a bottom of the insertion groove is closerto an inner face of the second panel than an opening of the insertiongroove to the edge groove.

The acute angle may be in the range of about 1° to about 30° andpreferably about 10°.

These angles may provide strong locking between a locking surface of theflexible tongue and a locking surface of the tongue groove

The insertion groove may extend along essentially the entire length ofthe edge groove.

The edge groove may extend along essentially the entire length of thesecond edge.

The flexible tongue is preferably displaceable in the insertion groove.

A core material of the first and the second panel may comprise a woodfibre based board, such as a HDF, MDF, plywood, solid wood orparticleboard, or a reinforced plastic board or a wood fibre compositeboard.

The core is preferably provided with a decorative layer.

An outer bevel edge of the edge tongue may be covered by a part of thedecorative layer.

The edge tongue may be configured such that when the tongue is formedout of the first panel, by e.g. mechanically cutting such as milling,the bevel with the decorative layer is maintained from a decorativelayer that covers a face of the core.

The bevel edge with the decorative layer may be an advantageous surfacefor the flexible tongue to be displaced along during the assembling ofthe first panel and the second panel.

The first edge may comprises a first edge surface which is parallel tothe junction plane, and the second edge may comprises a second edgesurface which is parallel to the junction plane, wherein the first edgesurface is configured to cooperate with the second edge surface.

The first edge surface or the second edge surface may comprise a recess.The recess may extend over the edge groove. A recess may alternativelybe provided at each side of the edge tongue. The recess may improve thecontact between the first edge surface and the second edge surface, withincreased pressure over a smaller area, and irregularities, such asloose fibres that remains from a mechanical cutting of the mechanicallocking system, in the first edge surface or the second edge surface iscompressed. A depth of the recess may be in the range of about 0.1 mm toabout 0.5 mm, preferably about 0.2 mm.

An outer corner at the junction plane of the first and the second panelmay comprise a bevel edge, preferably covered by a decorative layer. Thebevel may increase the strength of the corner. The decorative layer maybe a plastic foil, veneer or paint. The paint may be applied in aproduction line for mechanical cutting, such as milling, of themechanical locking system.

The flexible tongue may alternatively be arranged in an insertion groovein the edge tongue of the second edge of the second panel, and thetongue groove may be arranged in edge groove of the first edge of thefirst panel. However, a greater size of the insertion groove, ascompared to the tongue groove, may be required. Therefore, thealternative with the insertion groove in the edge section groove of thefirst panel may be the preferred alternative.

The flexible tongue may have a first displacement surface and anopposite second displacement surface which are configured to bedisplaced along a third displacement surface and a fourth displacementsurface, respectively, of the insertion groove.

A second aspect of the invention is an assembled product, such as afurniture or a furniture component, comprising the set of panels asclaimed described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will by way of example be describedin more detail with reference to the appended schematic drawings, inwhich:

FIG. 1 shows panels provided with a mechanical locking system accordingto an embodiment of the invention.

FIGS. 2A-2F show a flexible tongue according to an embodiment of thepresent invention.

FIGS. 3A-3B show a flexible tongue according to an embodiment of thepresent invention.

FIG. 3C shows an assembled furniture component according to anembodiment of the present invention.

FIGS. 4A-4C show assembling of panels provided with a mechanical lockingsystem according to an embodiment of the present invention.

FIGS. 5A-5C show assembling of panels provided with a mechanical lockingsystem according to an embodiment of the present invention.

FIGS. 6A-6B show panels provided with a mechanical locking systemaccording to an embodiment of the present invention.

FIGS. 7A-7D show panels provided with a mechanical locking systemaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows two panels 2, 4 that are arranged perpendicular to eachother and locked together. The two panels may be a part of a furnitureor a furniture component, such as a bookshelf, a cupboard, a wardrobe, abox, a drawer or a furniture component. The two panels may be a firstpanel 2 having a first main plane and a second panel 4 having a secondmain plane. The first panel 2 and the second panel 4 are provided with amechanical locking device for locking a first edge of the first panel 2to a second edge of the second panel 4, wherein the first main plane isessentially perpendicular to the second main plane. The first edge ofthe first panel 2 is locked to a second edge of the second panel 4 at ajunction plane J extending between the first main plane and the secondmain plane. The angle between the junction plane and the first mainplane is preferably about 45°. The first edge comprises an edge tongue22 that extends from the junction plane J. The edge tongue 22 extends inthis embodiment essentially perpendicular from the junction plane. Thesecond edge comprises an edge groove 21 at the junction plane J, whereinthe edge tongue is configured to cooperate with the edge groove forlocking together the first and the second edges in a first directionwhich is parallel to the junction plane J. The edge tongue 22 comprisesa tongue groove 10, and the edge groove 21 comprises a flexible tongue30 arranged in an insertion groove 20. The flexible tongue 30 isconfigured to cooperate with the tongue groove 10 for locking togetherthe first and the second edges in a second direction, which isperpendicular to the junction plane.

The edge tongue 22 at the junction plane 22 may comprises a firstsurface 41 and an opposite second surface 42, wherein the first and thesecond surfaces are parallel and preferably essentially perpendicular tothe junction plane J. The edge groove 21 at the junction plane maycomprises a third surface 40 and an opposite fourth surface 42, whereinthe third and the fourth surfaces are parallel to the first surface 41and to the second surface 43, wherein the first surface may beconfigured to cooperate with the third surface and the second surfacemay be configured to cooperate with the fourth surface for a locking inthe first direction.

The edge tongue 22 may comprises a fifth surface 45 and an oppositesixth surface 47 at the tip of the tongue, wherein the fifth and thesixth surfaces 45, 47 are parallel and preferably essentiallyperpendicular to the junction plane J. The tip may be in an area betweenthe tongue groove 10 and an outer most edge of the edge tongue 22. Theedge groove 21 may comprise a seventh surface 44 and an opposite eighthsurface 46 at a bottom of the edge groove, wherein the seventh and theeight surfaces 44, 46 are parallel to the fifth surface 45 and the sixthsurface 47. The fifth surface 45 may be configured to cooperate with theseventh surface 44 and the sixth surface 47 may be configured tocooperate with the eight surface 46 for a locking in the firstdirection.

The insertion groove 20 may be arranged at an acute angle 75 to thesecond main plane, wherein a bottom of the insertion groove is closer toan inner face of the second panel 4 than an opening of the insertiongroove 20 to the edge groove 21. The acute angle may be in the range ofabout 1° to about 30°, for example, about 5° to about 15°, andpreferably about 10°. The insertion groove 20 may, as an alternative, bearranged parallel to the second main plane. The insertion groove 20 mayextend along essentially the entire length of the edge groove 21 and theedge groove 21 may extends along essentially the entire length of thesecond edge.

A core of the first and second panel may be wood based. The edge groove21, the insertion groove 20, the edge tongue 22 and the tongue groove 10are preferably formed by mechanically cutting, such as milling, of thefirst panel 2 and the second panel 4, respectively.

The first panel 2 comprises an inner face 60 and an outer face 61 thatare preferably essentially parallel to the first main plane. The secondpanel 4 comprises inner face 62 and an outer face 63 that are preferablyessentially parallel to the second main plane. The inner face 60 of thefirst panel 2 and the inner face 62 of the second panel are preferablyconfigured to face toward an inside of an assembled product. A core ofthe first and second panel may be wood based and the core is preferablycovered with a decorative layer at the inner face and the outer face ofthe first and the second panel. The edge groove 21, the insertion groove20, the edge tongue 22 and the tongue groove 10 are preferably formed bymechanically cutting, such as milling, of the first panel 2 and thesecond panel 4, respectively.

The outer corner of the first panel and the second panel is preferablyprovided with a bevel 76 in order to increase the strength of themechanical locking system and cracks at the outer corner may be avoided.The bevel may extend through part of the core, and the bevel is for suchan embodiment preferably covered with a decorative layer.

An embodiment of the flexible tongue 30, which is displaceable in aninsertion groove 20, is shown in FIGS. 2A-2D. FIGS. 2A-2B show theflexible tongue 30 in a locked potion and FIGS. 2C-2D show the flexibletongue 30 during assembling of the first panel 2 and the second panel 4.FIG. 2B shows a cross section of the flexible tongue 30 in FIG. 2A. FIG.2D shows a cross section of the flexile tongue 30 in FIG. 2C. Theflexible tongue 30 comprises bendable protruding parts 24. A space 23 isprovided between the flexible tongue 30 and a bottom wall of theinsertion groove 20. FIG. 2C shows that the flexible tongue 30 is pushedinto the insertion groove 20 and towards the bottom wall of theinsertion groove 20 during assembly of the first panel 2 with the secondpanel 4. The flexible tongue 30 springs back toward its initial positionwhen the first panel 2 and the second panel 4 have reached a lockedposition. A recess 25 is preferably arranged at each bendable protrudingpart.

The flexible tongue 30 may have a first displacement surface 26 and anopposite second displacement surface 27, configured to be displacedalong a third displacement surface 28 and a fourth displacement surface29, respectively, of the insertion groove 20.

An alternative embodiment of the flexible tongue 30, without theprotruding bendable parts 24, is shown in FIGS. 2E-2F. FIG. 2F shows across section of the flexible tongue 30 shown in FIG. 2E. Thealternative embodiment is bendable in its length direction in order toaccomplish the same function as the embodiment shown in FIGS. 2A-2D.

A further embodiment of the flexible tongue 30 is shown in FIGS. 3A-3B.FIG. 3A shows the flexible tongue 30 before the first panel 2 and thesecond panel 4 are locked in the direction parallel to the second mainplane. The flexible tongue 30 comprises an inner part 31 provided withwedge elements and outer part for the locking of the first panel 2 andthe second panel 4 in the direction parallel to the second main plane.The locking is obtained by applying a force P, in a direction parallelto the first edge of the first panel 2, at a short edge of the outerpart. The force P displaces the outer part of the flexible tongue 30 inthe direction parallel to the first edge of the first panel 2 and thewedge elements force the outer part of the flexible tongue 30 in aperpendicular direction, out of the insertion groove 20. The resultingdisplacement, shown with arrow 32, of the outer part of the flexibletongue 30 is therefore in a direction between the direction parallel tothe first edge of the first panel 2 and the perpendicular direction.Each of the panels 2-6 may include a flexible tongue 30.

FIG. 3C shows an embodiment of an assembled product, such as furnitureor a furniture component, comprising the set of panels described above.The second edge of the first panel 2 is configured as the second edge ofthe second panel. The first edge of the second panel 4 is configured thesame, or essentially the same, as the first edge of the first panel 2.The first and the second panel 2, 4 are thereby configured essentiallyidentical. Two more panels are shown, a third panel 6 and a fourth panel5, each comprising a first and a second edge that are configured thesame, or essentially the same, as the first and the second edge of thefirst and the second panels 2, 4. The first, second, third and fourthpanels are assembled as a frame. Panels that each comprise a first and asecond edge that are configured essentially identical may be anadvantage since only one type of panels needs to be produced to enablethe assembling of wide variety of furniture or furniture components.

FIG. 4A-4C shows an embodiments of assembling the first 2 and the secondpanel 4. The first edge comprises a first edge surface 55, which isparallel to the junction plane J, and the second edge comprises a secondedge surface 54, which is parallel to the junction plane, wherein thefirst edge surface 55 is configured to cooperate with the second edgesurface 54. The first panel is displaced in a first displacementdirection D1, which is perpendicular to the junction plane. The edgetongue 22 is inserted into the edge groove 21 and the flexible tongue ispushed back into the displacement groove and springs back towards theinitial position when the first edge surface and the second edge surfaceare in contact. In an alternative assembling the second panel 4 isdisplaced in addition or as an alternative to the displacement of thefirst panel. The second panel is displaced in a second displacementdirection D2, which is opposite to the first displacement direction.

FIG. 5A-5B show that the flexible tongue 30 may alternatively bearranged in an insertion groove 20 in the edge tongue 22 of the secondpanel 4 and the tongue groove 10 may be arranged in edge groove 21 ofthe first edge of the first panel 2. However, a greater size of theinsertion groove 20, as compared to the tongue groove 10, may berequired. Therefore, the embodiment in FIG. 1 with the insertion groove20 in the edge groove 21 may be a preferred embodiment. The assemblingof the first and second panels in FIG. 5A-5C are essentially identicalto the assembling of the first and second panels in FIG. 4A-4C.

FIG. 6A-6B show/an embodiment comprising a recess 50 at the second edgesurface. Said recess may extend over the edge groove 21. In analternative embodiment (not shown in the drawings) the first edgesurface 55 is proved with a recess, preferably a recess at each side ofthe edge tongue 22. The recess may improve the contact between the firstedge surface and the second edge surface, with increased pressure oversmaller contacts areas 51, and irregularities, such as loose fibres thatremains from a mechanical cutting of the mechanical locking system, inthe first edge surface or the second edge surface are compressed. Adepth 75 of the recess 50 may be in the range of about 0.1 mm to about0.5 mm, preferably about 0.2 mm. The contact areas 51 are preferablyarranged adjacent the inner face and adjacent the outer face. Thecontact areas 51 may comprise 5-50%, or 10-35%, of the length of theedge surface.

An outer bevel edge of the edge tongue 22 may be covered by a part 64 ofthe decorative layer arranged on the inner face 60 of the first panel.The edge tongue may be configured such that when the tongue is formedout of the first panel, by e.g. mechanically cutting such as milling,the bevel with the decorative layer is maintained from the decorativelayer that covers a face of the core. The part 64 of the decorativelayer may therefore be in a same level L as the decorative layerarranged on the inner face 60 of the first panel.

The bevel edge with the decorative layer may be an advantageous surfacefor the flexible tongue to be displaced along during the assembling ofthe first panel and the second panel.

FIG. 7A-7D show an embodiment that may increase the strength of the edgetongue that may be advantageous for some core materials. A length 70 ofthe edge tongue is increased to obtain longer distance 71, preferably inthe range of about 40% to about 60%, preferably about 50% of thethickness 74 of the second panel 4, and more material between the tonguegroove and the tip of the tongue, as is shown in FIG. 7B, which is anenlarged view of the encircled area in FIG. 7C. The edge tongue isadapted to the thickness of the second panel by proving a bevel 72 atthe tip of the tongue. The bevel 72 is arranged at the side of the edgetongue that is opposite the side with tongue groove 10. A surface of thebevel is preferably essentially parallel to second main surface and abottom surface 73 of the edge groove is preferably parallel to the bevelsurface.

The core material of the panels and elements in the embodiments abovepreferably comprises a wood fibre based board, such as a HDF, MDF,plywood, solid wood or particleboard, a reinforced plastic board, or awood fibre composite board.

The invention claimed is:
 1. A set of panels comprising a first panelwith a first main plane and a second panel with a second main plane,wherein the first and the second panel are provided with a mechanicallocking device for locking a first edge of the first panel to a secondedge of the second panel at a junction plane, wherein the first mainplane is essentially perpendicular to the second main plane and thejunction plane is extending between the first main plane and the secondmain plane, wherein: the first edge comprises an edge tongue thatextends from the junction plane, and the first edge comprises a firstedge surface having a first section which extends parallel to thejunction plane on one side of the edge tongue and having a secondsection which extends parallel to the junction plane on an opposite sideof the edge tongue; the second edge comprises an edge groove at thejunction plane, wherein the edge tongue is configured to cooperate withthe edge groove for locking together the first and the second edges in afirst direction which is parallel to the junction plane; the edge tonguecomprises a tongue groove; and the edge groove comprises a flexibletongue arranged in an insertion groove, said flexible tongue isconfigured to cooperate with the tongue groove for locking together thefirst and the second edges in a second direction which is perpendicularto the junction plane.
 2. The set of panels as claimed in claim 1,wherein the angle between the junction plane and the first main plane isabout 45°.
 3. The set of panels as claimed in claim 1, wherein edgetongue extends essentially perpendicular from the junction plane.
 4. Theset of panels as claimed in claim 1, wherein the edge tongue at thejunction plane comprises a first surface and an opposite second surface,wherein the first and the second surfaces are parallel.
 5. The set ofpanels as claimed in claim 4, wherein the edge groove at the junctionplane comprises a third surface and an opposite fourth surface, whereinthe third and the fourth surfaces are parallel to the first surface andto the second surface, wherein the first surface is configured tocooperate with the third surface and the second surface is configured tocooperate with the fourth surface for a locking in the first direction.6. The set of panels as claimed in claim 5, wherein the third surfaceand the fourth surface extend perpendicular to the junction plane. 7.The set of panels as claimed in claim 4, wherein the first surface andthe second surface extend perpendicular to the junction plane.
 8. Theset of panels as claimed in claim 1, wherein the edge tongue comprises afifth surface and an opposite sixth surface at the tip of the tongue,wherein the fifth and the sixth surfaces are parallel.
 9. The set ofpanels as claimed in claim 8, wherein the edge groove comprises aseventh surface and an opposite eighth surface at a bottom of the edgegroove, wherein the seventh and the eight surfaces are parallel to thefifth surface and the sixth surface, wherein the fifth surface isconfigured to cooperate with the seventh surface and the sixth surfaceis configured to cooperate with the eight surface for a locking in thefirst direction.
 10. The set of panels as claimed in claim 1, whereinthe insertion groove is arranged parallel to the second main plane or atan acute angle to the second main plane, wherein a bottom of theinsertion groove is closer to an inner face of the second panel than anopening of the insertion groove is to the inner face of the secondpanel.
 11. The set of panels as claimed in claim 1, wherein theinsertion groove extends along essentially the entire length of the edgegroove.
 12. The set of panels as claimed in claim 1 wherein the edgegroove extends along essentially the entire length of the second edge.13. The set of panels as claimed in claim 1, wherein the flexible tongueis displaceable in the insertion groove.
 14. The set of panels asclaimed in claim 1, wherein a core material of the first and the secondpanel comprises a wood fibre based board.
 15. The set of panels asclaimed in claim 14, wherein the core is provided with a decorativelayer.
 16. The set of panels as claimed in claim 15, wherein an outerbevel edge of the edge tongue is covered by a part of the decorativelayer.
 17. The set of panels as claimed in claim 1, wherein the secondedge comprises a second edge surface which is parallel to the junctionplane, wherein the first edge surface is configured to cooperate withthe second edge surface.
 18. A set of panels comprising a first panelwith a first main plane and a second panel with a second main plane,wherein the first and the second panel are provided with a mechanicallocking device for locking a first edge of the first panel to a secondedge of the second panel at a junction plane, wherein the first mainplane is essentially perpendicular to the second main plane and thejunction plane is extending between the first main plane and the secondmain plane, wherein: the first edge comprises an edge tongue thatextends from the junction plane; the second edge comprises an edgegroove at the junction plane, wherein the edge tongue is configured tocooperate with the edge groove for locking together the first and thesecond edges in a first direction which is parallel to the junctionplane; the edge tongue comprises a tongue groove; the edge groovecomprises a flexible tongue arranged in an insertion groove, saidflexible tongue is configured to cooperate with the tongue groove forlocking together the first and the second edges in a second directionwhich is perpendicular to the junction plane; the first edge comprises afirst edge surface which is parallel to the junction plane, and thesecond edge comprises a second edge surface which is parallel to thejunction plane, wherein the first edge surface is configured tocooperate with the second edge surface; and the first edge surface orthe second edge surface comprises a recess.
 19. A set of panelscomprising a first panel with a first main plane and a second panel witha second main plane, wherein the first and the second panel are providedwith a mechanical locking device for locking a first edge of the firstpanel to a second edge of the second panel at a junction plane, whereinthe first main plane is essentially perpendicular to the second mainplane and the junction plane is extending between the first main planeand the second main plane, wherein: the first edge comprises an edgetongue that extends from the junction plane; the second edge comprisesan edge groove at the junction plane, wherein the edge tongue isconfigured to cooperate with the edge groove for locking together thefirst and the second edges in a first direction which is parallel to thejunction plane; the edge tongue comprises a tongue groove; the edgegroove comprises a flexible tongue arranged in an insertion groove, saidflexible tongue is configured to cooperate with the tongue groove forlocking together the first and the second edges in a second directionwhich is perpendicular to the junction plane; the edge tongue at thejunction plane comprises a first surface and an opposite second surface,wherein the first and the second surfaces are parallel; and the firstsurface and the second surface extend perpendicular to the junctionplane.